Noise-aware entanglement generation protocols for superconducting qubits with impedance-matched FBAR transducers

Abstract Connecting superconducting quantum processors to telecommunications-wavelength quantum networks is critically necessary to enable distributed quantum computing, secure communications, and other applications. Optically-mediated entanglement heralding protocols offer a near-term solution that can succeed with imperfect components, including sub-unity efficiency microwave-optical quantum transducers. The viability and performance of these protocols relies heavily on the properties of the transducers used: the conversion efficiency, resonator lifetimes, and added noise in the transducer directly influence the achievable entanglement generation rate and fidelity of an entanglement generation protocol. Here, we use an extended Butterworth–van Dyke (BVD) model to optimize the conversion efficiency and added noise of a Thin film bulk acoustic resonator (FBAR) piezo-optomechanical transducer. We use the outputs from this model to calculate the fidelity of one-photon and two-photon entanglement heralding protocols in a variety of operating regimes. For transducers with matching circuits designed to either minimize the added noise or maximize conversion efficiency, we theoretically estimate that entanglement generation rates of greater than <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>160</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mrow> <mml:mi>kHz</mml:mi> </mml:mrow> </mml:mrow> </mml:math> can be achieved at moderate pump powers with fidelities of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:mo>&gt;</mml:mo> </mml:mrow> <mml:mn>90</mml:mn> <mml:mi mathvariant="normal">%</mml:mi> </mml:mrow> </mml:math> . This is the first time a BVD equivalent circuit model is used to both optimize the performance of an FBAR transducer and to directly inform the design and implementation of an entanglement generation protocol. These results can be applied in the near term to realize quantum networks of superconducting qubits with realistic experimental parameters.